package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    /**
     * 根据id查询商铺信息
     * @param id 商铺id
     * @return 商铺详情数据
     */
    @Override
    public Result queryById(Long id) throws InterruptedException {
        
       //缓存穿透
        Shop shop = queryWithPassThrough(id);
//        Shop shop = cacheClient.queryWithPassThrough(
//                CACHE_SHOP_KEY,
//                id,
//                Shop.class,
//                this::getById,
//                CACHE_SHOP_TTL,
//                TimeUnit.MINUTES);

        //互斥解决缓存击穿
//        Shop shop = queryWithMutex(id);
//        if(shop == null){
//            return Result.fail("店铺不存在");
//        }

//        //逻辑过期解决缓存击穿
//        Shop shop = queryWithLogicalExpire(id);
//        if(shop == null){
//            return Result.fail("店铺不存在");
//        }

        //7.返回
        return Result.ok(shop);
    }

    //解决缓存穿透问题方法
    private Shop queryWithPassThrough(Long id){
        //1.从redis查询商品缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //2，判断是否存在
        if(StrUtil.isNotBlank(shopJson)) {
            //3.存在直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //。。如果是空值，返回错误信息，不会请求到数据库，解决缓存穿透问题。
        //。。但可能会造成数据短期不一致问题，解决方案是数据库新增后加入缓存覆盖空值。
        if(shopJson != null) {
            return null;
        }
        //4.不存在，查询数据库
        Shop shop = getById(id);

        //5.不存在，返回错误
        if (shop == null) {
            //。。解决缓存穿透问题，设置空缓存
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
//            return Result.fail("店铺不存在");
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7.返回
        return shop;
    }

    //互斥解决缓存击穿
    private Shop queryWithMutex(Long id) throws InterruptedException {
        //1.从redis查询商品缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //2，判断是否存在
        if(StrUtil.isNotBlank(shopJson)) {
            //3.存在直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //。。如果是空值，返回错误信息，不会请求到数据库，解决缓存穿透问题。
        //。。但可能会造成数据短期不一致问题，解决方案是数据库新增后加入缓存覆盖空值。
        if(shopJson != null) {
            return null;
        }

        //4实现缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //4.2判断是否成功
        if(!isLock){
            //4.3失败则休眠并重试
            Thread.sleep(50);
            return queryWithMutex(id);
        }
        //4.4成功则查询数据库
        Shop shop = getById(id);
        //5.不存在，返回错误
        if (shop == null) {
            //。。解决缓存穿透问题，设置空缓存
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
//            return Result.fail("店铺不存在");
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //释放锁
        releaseLock(lockKey);
        //7.返回
        return shop;
    }
    private boolean tryLock(String key){
        //redis中的setnx，只有不存在才会设置成功
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key,
                "1",
                10,
                TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);

    }
    private void releaseLock(String key){
        stringRedisTemplate.delete(key);
    }


    //逻辑过期解决缓存击穿
    private Shop queryWithLogicalExpire(Long id) throws InterruptedException {
        //1.从redis查询商品缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //2，判断是否存在
        if(StrUtil.isBlank(shopJson)) {
            //3.不存在直接返回
            return null;
        }

        //4.命中.需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((String) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5.判断逻辑日期是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期直接返回信息
            return shop;
        }

        //5.2过期获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);

        //5.2.1获取成功开启独立线程实现缓存重建，并返回原信息
        if(isLock){
            //5.2.1.1开启独立线程
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //5.2.1.2写入redis
                    saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //5.2.1.3释放锁
                    releaseLock(lockKey);
                }
            });

        }

        //5.2.2获取失败，直接返回原信息
        return shop;

    }

    //创建线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);




    public void saveShop2Redis(Long id, Long expireSeconds) {
        //1.查询店铺数据
        Shop shop = getById(id);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }


    @Override
    @Transactional
    public Result update(Shop shop) {

        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }

        //1.更新数据库
        updateById(shop);

        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
